Diels–Alder adducts of a labdane diterpenoid from the Chinese liverwort Pallavicinia subciliata

• Published in: Organic chemistry frontiers an international journal of organic chemistry Vol. 9; no. 7; pp. 1790 - 1796
• Main Authors: Shu-Gong, Liu, Chun-Yang, Zhang, Jin-Chuan Zhou, Jing-Jing, Han, Ming-Zhu, Zhu, Jiao-Zhen Zhang, Li, Yi, Ze-Jun Xu, Meng, Hui, Wang, Xue, Zong, Yan, Shuang-Zhi Yuan, Ya-Nan Qiao, Ya-Jie Tang, Hong-Xiang, Lou
• Format: Journal Article
• Language: English
• Published: London Royal Society of Chemistry 29.03.2022
• Subjects: Adducts; Aquatic plants; Carbon radioisotopes; Crystal structure; Diels-Alder reactions; Dimers; Diterpenes; Inflammation; Lipopolysaccharides; Macrophages; Organic chemistry; Pallavicinia; Single crystals
• DOI: 10.1039/d1qo01891d
• ISSN: 2052-4110

A 7,8-seco-2,8-cyclolabdane diterpenoid, pallasubcin A (1), and three rare pallasubcin A-derived dimers, pallasubcins B–D (2–4), formed via a Diels–Alder reaction between C-12–C-14′ and C-15–C-15′ were isolated from the Chinese liverwort Pallavicinia subciliata. Their structures were elucidated by comprehensive spectroscopic analysis, X-ray single crystal diffraction, and ECD calculations. Plausible biogenetic pathways are presented for all compounds. Preliminary anti-inflammatory determinations showed that compound 2 exhibited strong activity under nontoxic concentrations with a 73.03% (25 μM) maximum inhibition rate of NO production on LPS-induced RAW 264.7 murine macrophages.